Tony Blair was today warning unions they cannot "veto" plans for private sector involvement in public services.

In a speech being trailed as a "route map for reform", the Prime Minister will spell out his "absolute determination" to push through the changes.

His hardline approach will put him on a collision course with union leaders, who are extremely wary of the private sector agenda.

They issued fresh warnings last night about the "privatisation" of the NHS and schools and called on Mr Blair to clarify his intentions.

Unison general secretary Dave Prentis said: "We want to engage in a genuine dialogue about how to improve delivery."

Bill Morris, general secretary of the Transport and General Workers Union, said they would defend public services in the workplace and at the ballot box if necessary.

The GMB was waiting to hear Mr Blair's speech before deciding which of two pre-prepared advertisements to use in a £250,000 campaign.

A union spokesman said: "We will be looking for a guarantee from Tony Blair that he will allow this issue to be debated on the floor of the Labour party conference."

Updated: 11.03 Monday, July 16